The present invention relates to a heat engine comprising a system for varying compression ratio of said engine provided with a stepped intermediate pinion.
Document EP14163870.0 teaches to realise a system for varying compression ratio as a function of engine operating conditions. This system for varying compression ratio comprises an assembly of eccentric parts mounted on the crankpins of the crankshaft in a manner that each cooperates with an end of the connecting rod.
A control device 1 shown in FIG. 1 allows to control the position of the eccentric parts 2. For this purpose, the control device 1 comprises an actuating shaft 3 and a cascade of pinions formed by an actuating pinion 4 attached to the actuating shaft 3, and intermediate pinions 5 of which one portion mesh with the actuating pinion 4 and the other portion with a gear 6 that is attached to the eccentric part 2.
During operation and when the actuating shaft 3 is rotationally fixed with respect to the frame, the system has a configuration at fixed compression ratio. Upon changing compression ratio, the angular position of the eccentric part 2 is controlled by the angular position of the actuating shaft 3 so as to move to a new compression ratio. For this purpose, through the pivots of the crankshaft, the shafts and so-called transfer gears transmit the kinematics of the eccentric part 2 located on the side of the actuating shaft 3 from one to the other towards all the other eccentric parts 2 of the crankshaft (not visible in FIG. 1).
However, the problem of such a configuration is that the shift of the gear planes between firstly the actuating pinion 4 and the intermediate pinions 5 and secondly between the intermediate pinions 5 and the gear 6 requires digging a flange of the crankshaft to integrate the actuating pinion 4 and a portion of the intermediate pinions 5, which locally weakens the crankshaft.
In addition, the balancing of the crankshaft may require reduction of the opposite flange, which also tends to reduce the mechanical strength of the crankshaft. Machining the recess or recesses in the flange also results in a significant machining time that can generate many chips.